Connecting MC4 to Box

DavidOH · October 2011

Now that I have it, how do I put it together.

MC4 cables
http://www.solar-electric.com/6fomc4so2exc.html
Combiner Box
http://www.solar-electric.com/mnpv6.html

If someone else has this setup how do you make the connection?
Will I have to cut the ends off of the cables and wire them to the buss?

mike95490 · October 2011

Re: Connecting MC4 to Box

DavidOH wrote: »

...Will I have to cut the ends off of the cables and wire them to the buss?

NO !!

You purchase a MC4 jumper cable, connect it to the panels, and cut it (the jumper) in half, leaving you cables you can connect in the box.

The factory MC4 connectors are part of the panel warranty, cut them off, and you have no warranty.

Also, the MC4 connectors lock, so you may need an unlock tool to disconnect.

And MC4 is not rated for "make or break". you have to have no power in the DC side when connecting, or you will arc weld the gold contacts

BB. · October 2011

Re: Connecting MC4 to Box

So, take the Male/Female MC4 cables and cut them in 1/2--Plug the MC4 into your panels and wire the cut ends into your wiring/distribution box (as needed).

Disconnect Tool for MC4 Connectors (set of 2)

Price: $9.00

-Bill

DavidOH · October 2011

Re: Connecting MC4 to Box

I have the unlock tool. NAW&S did not tell me about a jumper cable. :grr
I did not see one.

I do not want to cut them. That defeats the purpose of having connector cables.
Please tell me where they are available.

BB. · October 2011

Re: Connecting MC4 to Box

You can use the cable in your link (8' male/female) and cut them in 1/2 (add your own appropriate wiring for longer runs):

http://www.solar-electric.com/6fomc4so2exc.html

They sell other lengths too (longer):

http://www.solar-electric.com/incaforsoelp.html

And they probably can make shorter/custom lengths too (I don't work for NAWS--You will have to contact them directly for details.

-Bill

DavidOH · October 2011

Re: Connecting MC4 to Box

Clarification:
I HAVE CABLES!

4 panels, 2 - 8ft cables, 2 - 15 ft cables.
1 box.

NO way will I cut/modify the panels.
I am asking if I need to cut the ends off of the 8 and 15 ft cables.
Not the cable attached to the panel.

I have not seen any cable that will connect the MC4 end to the buss bar in the box.
I would have gotten a pre-wired box if they had them with breakers.
http://www.solar-electric.com/prpvcobo.html

Thanks Bill. I called NAW&S and that is what they told me to do.

I should have bought 2 - 30ft cables and cut them in half.
Thanks for nothing NAW&S now I have 4 cables the exact length that I have to cut.

BB. · October 2011

Re: Connecting MC4 to Box

I am a little confused... you have male/female cables--just cut in 1/2. MC4 connects to panel(s) and the cut end to your box/wire nut/bus bar as needed.

The boxes you pointed to are actually wired with MC4 inputs--So, if you have one of those boxes, you should just need to attach the "whole jumper" from panel to box (assuming the male/female cable ends match up correctly).

Note about touch safe fuse holders (if your box has them). They should not be used as disconnect "switches" while under load. In some cases, just popping open the fuse holder while under load can strike an arc--which will melt the fuse holder block (DC current sustains arcs very nicely compared to AC current/power).

-Bill

DavidOH · October 2011

Re: Connecting MC4 to Box

Thanks Bill for the reply.

TnAndy · October 2011

Re: Connecting MC4 to Box

The panels come with cables (2-4' long, depending on manufacturer ) with MC connectors.

You buy extension cables to run from the panel connectors to the combiner box. 15' or less from the panel, you buy a 30' extension cable, and cut it in half.

Plug the MC connectors together, and the cut ends go in the buss bar(neg) and breakers(pos) in the combiner box.

By the way, I find I can easily unlock an MC-4 locking connector with a pair of small pliers squeezing the locking tabs inward and pulling apart.....no special tool needed.

Also, depending on your charge controller, you can often run panels in sets of 2-3-4(or more) in series and minimize your need for extension cables....for example, I have 10 panels on an array, wired in pairs of 2 in series, and only need 5 extension cables. Had I put 9 on an array, I could have wired in sets of 3, then only needed 3 extension cables and a 3 space/breaker combiner box. Depends on the limits IN on your charge controller.

DavidOH · October 2011

Re: Connecting MC4 to Box

mike90045 wrote: »

NO !!

You purchase a MC4 jumper cable, connect it to the panels, and cut it (the jumper) in half, leaving you cables you can connect in the box.

YES!!!!!!!!!!!!!

Northern Arizona Wind and Sun told me to cut the cables.
Exactly as I thought.
If I had know that I would have only bought two extra long ones instead of four.

waynefromnscanada · October 2011

Re: Connecting MC4 to Box

DavidOH wrote: »

YES!!!!!!!!!!!!!

Northern Arizona Wind and Sun told me to cut the cables.
Exactly as I thought.
If I had know that I would have only bought two extra long ones instead of four.

Mike was saying "NO" to cutting the cables on your panels, (as that would void your panel warranty). He was saying to cut your extension cables in half, that would give you 2 cables, each with a proper end on it, for each extension cable you cut in half. There's been a lot of misunderstandings happing in this thread for some reason.

DavidOH · October 2011

Re: Connecting MC4 to Box

Quite a lot of misunderstanding.

He lost me with "jumper cable" instead of calling it an MC4 cable.

I guess I will go with my first thought and cut the ends off of all four cables, then wire them into the box.

I have the circuit breakers that were recommended; 12 amp.

petertearai · October 2011

Re: Connecting MC4 to Box

Maybe slightly off topic, but why is the panel warranty void if cut , surly if done with a watertight connection it should be OK. I have just purchased a suntek 190 and asked the supplier re the cutting of leads, the rep said they would not void the warranty if the leads were cut. Having said all that , in most instances you would not want to cut off the MC4 connectors.

niel · October 2011

Re: Connecting MC4 to Box

for what pv make do they allow the cutting of the mc4 connectors without voiding the warranty?

petertearai · October 2011

Re: Connecting MC4 to Box

Sunteck 190 mono 24volt nominal ................

petertearai · October 2011

Re: Connecting MC4 to Box

To be more precise Suntech STP190s-24/Ad+ .
Looking at the install guide and warranty guide I cant see anything that specifically says do not cut off your MC4 convectors. Maybe I will have another look through.

Cariboocoot · October 2011

Re: Connecting MC4 to Box

They won't put it in the instructions. It will be in the warranty fine print. It will say something about not "altering the panel". It is actually very sensible, because once you cut the polarized connectors off it becomes amazingly easy to wire them up backwards. This can result in damage to the panel, depending on the circumstances.

petertearai · October 2011

Re: Connecting MC4 to Box

My BP panels don't have leads, only a connection box.They would by the same rational be easy to reverse.

Cariboocoot · October 2011

Re: Connecting MC4 to Box

petertearai wrote: »

My BP panels don't have leads, only a connection box.They would by the same rational be easy to reverse.

Yep, they would.
But at least you wouldn't have "altered" the panel.
The difference between engineers and lawyers. :roll:

DavidOH · October 2011

Re: Connecting MC4 to Box

petertearai wrote: »

Maybe slightly off topic, if done with a watertight connection it should be OK.

Not off topic. I have the popular KD135 panels. I purchased the water tight box.
Midnite Solar MNPV6 along with the recommended cables.

"The KD135 solar panel comes with two MC4 (latching) cable leads, you will need to purchase at least one MC4 extension cable to plug into the connectors."

I was thinking when I bought them that they would PLUG Directly into the box.
Nope! Not that easy. Sigh....

As far as that goes, the possibility exists that I could still wire them incorrectly IN THE BOX.

Now I thought about purchasing additional ends and wiring them in the box, so I would not have to cut the cables, but that would be about another $30.

10 pairs MC4 male & female connector
http://www.ebay.com/itm/110738261244?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Now that I am thinking about that more....
I may just modify the box so that is IS a plug in box.

Running wire from the buss bars to four female plug ends should make me a box that is quickly connected to any panel with an MC4 connector of any length.

As long as I get the connections on the inside of the box wired right there should never be a problem making a connection. :cool:

Any thoughts on this?
You guy are great here. Thanks for you input.

Cariboocoot · October 2011

Re: Connecting MC4 to Box

My thought is: it's about time some company got their act together and made combiner boxes that have the MC4 connectors inside already attached to a negative bus bar and a positive fuse rack (separate fuse for each string for multiple parallel connections). Cost more? Yes, but as opposed to buying separate cables, cutting them, hooking up the wire ends to screw terminals ... maybe not. Two such terminals for the down lead capable of handling some big wire (like 4 AWG) and you're done.

TnAndy · October 2011

Re: Connecting MC4 to Box

Well, here's the problem with having the connectors made IN the combiner box:

How are you gonna get the connector THRU any kind of weathertite adapter and knockout ?

What you do now is get a 1/2 male adapter, with a rubber plug in it that has a couple holes sized for #10 wire. Once you cut the extension cable, the cut ends feed tight thru those holes ( one adapter and knockout per cable extension ). I can't see any practical way to feed a BIG MC4 end thru an adapter, and then have it close back down to a SMALL #10 wire size......LOT of silicone caulk I guess ?

Second point: Every install is different. If you have connectors in a box, and use anything BUT custom made extension lengths, you're gonna have wire leftover to deal with.....whereas now, you plug in the male/female ends of the MC4's, and cut the other end to whatever length you need.....no extra wire to have to bundle up and do something with....

And cost more ? Wow....I'd say. To get a dozen MC4 connectors in a combiner box ( 6 pos/6 neg ) like the Midnite 6 slot box, they'd probably have to double the size of the box......then you're paying for 12 connectors in the box, and another 12 on the wire ends.....that's 24 MORE connectors....for what ? So you don't have to screw a screw down on a stripped wire ?? Really ??

The only real purposes of any MC connector AT ALL is:

1. Make the junction point at the panel sealed at the factory, so no corrosion gets in.

2. Make it a little easier/quicker to series panels together......most grid tie installs, you series 10-15-20 panels together up on the racking, and only come off with ONE extension cable, at about 300-500v down to the inverter......there IS no combiner box.

3. To make is a bit more "Murphy Proof" on the pos/neg connections.

Cariboocoot · October 2011

Re: Connecting MC4 to Box

Right. Better just give up on the whole thing. No sense trying to make a better, more convenient product.

If engineers took that attitude we'd still be pushing things along on logs.

MC4 connectors are not that much larger than the cable they serve. You can put them through rubber "squeeze" seals and tighten them down afterward.

Not likely to be lots of wire left over on an install as the extensions come (and can be made in) different lengths. You would have accurate distances for calculating V drop.

Costs are variable. What is expensive today may be cheap tomorrow, especially when mass produced (uniform product). The industry needs more consolidated standards, not fewer.

MC4 connectors are more reliable than screw terminals because you can not "tighten them wrong".

Not every install is a single string grid-tie unit. You're leaving out a major portion of the industry that could benefit from such a product.

Absolutely nothing is "Murphy proof".

Such self-imposed limitations as you apply would not get you far in an industry that is still ripe for innovation.

rick · October 2011

Re: Connecting MC4 to Box

MidNite Solar builds and designs their combiner boxes with an MC4 connector option. We sell them.

http://www.solar-electric.com/prpvcobo.html

TnAndy · October 2011

Re: Connecting MC4 to Box

Hey....the market determines what works.

How many get sold AT TWICE THE PRICE of a regular box ?

Plain Jane 6 circuit box for $87.20 or a fancy 4 circuit for $159, or if you need more than 4, you step up to the 8 space box for $287.......two hundred bucks more + MC connectors on both ends of the extension cable......what, about 3 times the price ?

I notice they are 'special order'......ahahahaaaa

Cariboocoot · October 2011

Re: Connecting MC4 to Box

rick wrote: »

MidNite Solar builds and designs their combiner boxes with an MC4 connector option. We sell them.

http://www.solar-electric.com/prpvcobo.html

Huzzah!

If you're paying for the install that could save its value in labour costs.

I was even thinking that since the MC4 connectors are water-tight they could be in rows outside the box (fastened to the side) with "dummy caps" for the unused ones: smaller box, no worries about leaking on the wire pass-through.

It never pays to limit the possibilities.

DavidOH · October 2011

Re: Connecting MC4 to Box

rick wrote: »

MidNite Solar builds and designs their combiner boxes with an MC4 connector option. We sell them.
http://www.solar-electric.com/prpvcobo.html

Yes, I noticed that the day I RECEIVED my order. They were not on the website before that. :grr

Those have fuses and not the breakers that I now have.
I would have paid extra to get my box already wired with the breakers and MC4 connectors added.
That is what I plan on making. MidNite Solar MNPV4-MC4 Solar Array Combiner
Same box. That has 4 fuses. Mine will have 6 breakers in the same box. :cool:

Vic · October 2011

Re: Connecting MC4 to Box

Great to see that MN is still at the the top of their game. Very aggressive in offering new, useful products, even a conectorized Combiner for Tyco connectors.

The only nit I have to pick, is that in the N AZ listing, it is stated that this Combiner is "100% Waterproof". Believe that 3R enclsures are "Rain-Tight". Will shed most falling rain, sleet, snow hail etc. They shed most water. The fact that they are NOT waterproof is a benefit, as they have some ventilation, which allows some of the wind-blown rain, condensation etc to evaporate.

There are gasketed NEMA enclosures, which generally, IIRC, even have a couple of weep holes or similar.

But someone else will pick my nit. Vic

BB. · October 2011

Re: Connecting MC4 to Box

Agree, big difference between weather and water proof.

-Bill

rick · October 2011

Re: Connecting MC4 to Box

TnAndy wrote: »

Hey....the market determines what works.

How many get sold AT TWICE THE PRICE of a regular box ?

Plain Jane 6 circuit box for $87.20 or a fancy 4 circuit for $159, or if you need more than 4, you step up to the 8 space box for $287.......two hundred bucks more + MC connectors on both ends of the extension cable......what, about 3 times the price ?

I notice they are 'special order'......ahahahaaaa

Well, we do sell them. They are special order because we don't stock them. Our warehouse only has so much room and we have to decide which items make the most sense to stock. If you do the math, the pre-wired combiner boxes are not as expensive as you're making them out to sound.

Standard MNPV6: $87.20
4 fuse holders: $23.00
4 fuses: $27.40
4 MC4 connectors: $20.00
Copper wire: $3.00

That adds up to a total of $160.60 and that does NOT include the labor cost to build the unit. The people building these could easily charge $65 to $75 per hour for labor. Plus, a pre-wired combiner box can significantly decrease your install time which usually saves additional money. So it actually makes good sense.

rick · October 2011

Re: Connecting MC4 to Box

Vic wrote: »

Great to see that MN is still at the the top of their game. Very aggressive in offering new, useful products, even a conectorized Combiner for Tyco connectors.

The only nit I have to pick, is that in the N AZ listing, it is stated that this Combiner is "100% Waterproof". Believe that 3R enclsures are "Rain-Tight". Will shed most falling rain, sleet, snow hail etc. They shed most water. The fact that they are NOT waterproof is a benefit, as they have some ventilation, which allows some of the wind-blown rain, condensation etc to evaporate.

There are gasketed NEMA enclosures, which generally, IIRC, even have a couple of weep holes or similar.

But someone else will pick my nit. Vic

I suppose that is technically correct. I'm going to update the website so that it says weatherproof. But that was why I included the text, "...when installed according to the manufacturer's instructions." If installed the way that MidNite solar explains, rain, snow, ice, or any other type of water cannot enter the enclosure. NEMA 3R will not protect against pressurized water though. If someone sprays the box with a high pressure garden hose or something, a NEMA 3R probably won't protect the insides. I think NEMA 4 is the rating for waterproof.

Connecting MC4 to Box

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